Multi-stage creep behavior of frozen granular soils: experimental evidence and constitutive modeling

The significance of ground freezing is becoming ever more germane as the design of new urban tunneling systems requires more complex geometries and higher bearing capacities, which are limited with conventional construction methods. Ground freezing is an advanced construction technique to make the water-saturated subsoil impermeable and temporarily increase its strength and stiffness. This study reports experimental investigations consisting of single-stage and multi-stage creep tests under uniaxial loading. The comparison of the different loading types reveals the influence of the stress–strain history on the rate- and temperature-dependent behavior of frozen granular soils. We extend the constitutive model for frozen soils proposed by Cudmani et al. (2022, Géotechnique, doi:10.1680/jgeot.21.00012) to consider stepwise loading and creep by coupling creep time with stress–strain history. Moreover, we simulate element tests and compare the simulations with our own experimental data as well as data from the literature to achieve the first step in validating the extended model. The good agreement of the numerical and experimental results confirms the constitutive model’s ability to capture the main features of the complex mechanical behavior of frozen granular soils for single-stage as well as multi-stage loading under constant temperatures.